What is Sunscreen?

Sunscreen protects the skin from absorbing ultraviolet (UV) rays. There are two kinds of UV rays that can affect the skin: UVA and UVB. In the U.S., sunscreen is considered an over-the-counter drug and is regulated by the U.S. Food and Drug Administration. Per FDA regulations, sunscreen can only be called “broad spectrum” if it protects against both UVA and UVB. 

Two Types of Sunscreen

Sunscreens can be broadly classified into two groups: physical blockers and chemical absorbers. 

Physical Blockers

Physical blockers work by reflecting or scattering UV light, preventing the UV light from hitting your skinThey are effective at protecting against both UVA and UVB radiationThey remain on the surface of your skin and are not readily absorbed into the skin. Physical blockers begin to work as soon as they are applied to the skin.  The two most common physical blockers are titanium dioxide and zinc oxide. Physical blockers are also called inorganic or mineral sunscreens. 

Chemical Absorbers

Chemical absorbing sunscreens—also called organic sunscreens—work by absorbing ultraviolet (UV) light. They allow the UV light to hit the skin but transform it into a non-harmful wavelength of light. Unlike physical blockers, chemical sunscreens do absorb into the skin. They take about 15 minutes to absorb into the skin, so they should be applied 15 minutes prior to any sun exposure in order to work effectively. They often contain multiple chemical ingredients. The chemicals can be differentiated by the type of rays they absorb: UVA, UVB, or both UVA and UVB.

Combination Sunscreens

Some sunscreens are a combination of physical blockers and multiple chemical absorbers.

What Does SPF Stand For?

SPF stands for Sun Protection Factor and refers to the level of sunburn protection provided by the sunscreen product. All sunscreens are tested to measure the amount of UV radiation exposure it takes to cause sunburn when using a sunscreen vs. when not using a sunscreen. The higher the SPF, the greater the protection is from UV radiation, and the greater the sunburn protection. Most people assume that SPF relates to a timeframe of protection. For example, it’s a common belief that an SPF of 30 would theoretically allow you to stay in the sun 30 times longer than you could without protection. But the FDA reminds us that the amount of UV exposure isn’t the same as the amount of time spent in the sun. Why? Because radiation exposure is greater at 1pm than 9am; greater in Florida than in North Dakota; and greater in summer than in winter. Additionally, you and your sunscreen affect the amount of UV exposure you receive: You may not put on enough sunscreen or you may miss areas; water and sweat wash the sunscreen off; towels and other fabrics rub sunscreen off. In all cases, sunscreens are effective for no more than two hours—and all of the above circumstances contribute to how much UV exposure you will receive.

AIM recommends that you use a broad-spectrum sunscreen of SPF 30 or higher daily on all exposed skin and reapply it at least every two hours, as well as after swimming, sweating, or towel drying.

Because SPF values are determined from a test that measures protection against sunburn caused by UVB radiation, SPF values only indicate a sunscreen’s protection from UVB—the kind of radiation that causes sunburn, damages the skin, and can contribute to developing melanoma.

Currently, there is no internationally agreed-upon test for measuring UVA protection in human skin. An estimate is made by a laboratory test in which the proportion of radiation passing through a measured amount of sunscreen is determined. To ensure some protection against UVA, products with physical blocking agents making up some of the active ingredients are recommended.

Here’s how your sun protection looks with each level of SPF:

SPF 15 – filters about 93% of UVB rays
SPF 30 – filters about 97% of UVB rays
SPF 50 – filters about 98% of UVB rays
SPF 100 – filters about 99% of UVB rays

To get the most protection, you want a broadspectrum sunscreen—these protect against UVB and UVA rays. UVA rays are long enough to reach the skin’s dermal layer, damaging collagen, and elastic tissue. That layer is also where the cells that stimulate skin darkening are found; that’s why UVA rays are considered the dominant tanning rays. (UVA rays are what is found in tanning beds and other tanning devices.) Though many people still think a tan looks healthy, it’s actually a sign of DNA damage—the skin darkens in an imperfect attempt to prevent further injury, which can lead to the cell mutations that can lead to melanoma. 

Sunscreen should be just one of the sun protection strategies you use to protect your skin. You also need to cover up with clothing and a hat, seek the shade, and try to stay out of the sun during peak hours, which are from 10:00 am to 4:00 pm. 

Applying Sunscreen Correctly 

Apply enough sunscreen to cover all exposed skin. Most adults need about one ounce — the amount in a shot glass — for full-body protection. Don’t forget to apply it to your ears, hands, feet, the back of your neck and any part of your scalp that isn’t covered by hair. Make sure to apply to the underside of your chin, which can be exposed to reflected sunlight. Remember: most people don’t apply enough sunscreen, so it’s okay to use more than you think you should. Many people wait to put on sunscreen when already outside, but you should apply it before you go in the sun. Chemical sunscreens need approximately 15 minutes to absorb into your skin and begin working. And don’t forget to wear sunscreen even on cloudy days and during the winter months. UV rays can still harm your skin when it’s cloudy outside. Finally, check the expiration date on your sunscreen to make sure it is not out of date. If your sunscreen changes consistency, becomes watery, separates, or changes color, even if it has not expired, it should be discarded. Sunscreen should not be left in direct sunlight or a hot environment like a car, as the heat can break down the chemicals in the sunscreen.  

No Sunscreen is Waterproof or Sweatproof 

Manufacturers of sunscreen cannot make claims that sunscreens are “waterproof” or “sweatproof.” Instead, sunscreen labels may say “water-resistant” and must specify whether they protect the skin for 40 or 80 minutes of swimming or sweating based on standard testing, according to the FDA. Always reapply sunscreen immediately after swimming, sweating, or toweling.



When To Reapply

one ounce of sunscreen at least every two hours, even if you haven’t been sweating or swimming. Cover all of your skin that will be exposed to the sun, including often neglected areas like your back, your ears, and behind your knees. 



Keep Babies Out of the Sun 

Sunscreen may be used on babies older than six months, but the skin on a baby is less mature compared to adults, and infants have a higher surface-area to body-weight ratio compared to older children and adults. Therefore, babies need to be physically protected by keeping them out of the sun and in the shade as much as possible. If there’s no natural shade, create your own with an umbrella, pop-up tent, or the canopy of the stroller. Make sure your baby wears a hat that provides sufficient shade at all times and clothing that covers and protects sensitive skin. Consult your pediatrician before using any sunscreen on your baby.

A Digital Magazine Devoted to Sunscreen

Why Has Sunscreen Been in the News Lately?

Sunscreen has been in the news lately relating to two different issues.

One issue is whether the chemicals in chemical sunscreen (not physical blockers/mineral sunscreen) are systemically absorbed in the body after application and, if so, whether there is any danger to the consumer.

In January 2020, the Journal of the American Medical Association reported the results of a study (a follow-up to a previous study) to assess whether, and to what extent, certain chemical sunscreen ingredients are absorbed into the body through the skin. This study tested six chemical sunscreen ingredients—avobenzone, homosalate, octinoxate, octisalate, octocrylene, and oxybenzone—in four different formulations to analyze the ingredients’ absorption levels in the blood.

Janet Woodcock of the FDA said, when announcing the study, “Results from our study released today show there is evidence that some sunscreen active ingredients may be absorbed. However, the fact that an ingredient is absorbed through the skin and into the body does not mean that the ingredient is unsafe, nor does the FDA seeking further information indicate such. Rather, this finding calls for further industry testing to determine the safety and effect of systemic exposure of sunscreen ingredients, especially with chronic use” (italics added).

And she stated clearly: “The FDA urges Americans to use sunscreens in conjunction with other sun protective measures (such as protective clothing).”

This study looked at chemical sunscreen ingredients. These chemicals are not present in mineral sunscreens (physical blockers), so if you have a concern about these findings, the use of mineral-based sunscreen is a simple alternative.

Sunscreen has also been in the news because of claims that certain ingredients in chemical sunscreen may damage the marine environment, specifically coral reefs.

Hawaii has banned (starting in 2021) oxybenzone and octinoxate, two ingredients found in many chemical sunscreens.

A few years ago, there was a flurry of media reports about studies that connected several chemical sunscreen ingredients to reef damage such as slowing coral growth and increasing the rate of coral bleaching. In 2018, the International Coral Reef Initiative came out with a review of studies related to sunscreen and coral reefs called Impacts of Sunscreens on Coral Reefs. The finding was that “further research is needed to better understand which ingredients are safe and which pose a realistic threat to marine ecosystems,” but that oxybenzone “has been identified as the main substance of concern.”

The report concluded that further research is needed because “there is a lack of firm evidence of widespread negative impacts at reef community and/or ecosystem level. The evidence available may not properly reflect conditions on the reef, where pollutants may rapidly disperse and be diluted. Concentrations of UV filters used in experimental work have generally been higher than those likely to been countered in the reef environment, although no study has assessed the levels of these chemicals in the tissues of long-lived species.”

Still, the report recommends that because reefs are already stressed, “a proactive and precautionary approach is required,” and suggests multiple measures that can be taken, including encouraging manufacture and promoting use of reef-friendly sunscreens.

The U.S. Congress is aware of the data gaps and has directed the EPA to work with the National Academy of Sciences to “conduct a review of the scientific literature of currently marketed sunscreens’ potential risks to the marine environment…and the current scientific literature on the potential public health implications associated with reduced use of currently marketed sunscreen ingredients for protection against excess ultraviolet radiation.”

For those concerned about the potential for reef damage, or for those traveling to or living in Hawaii, there are many chemical sunscreens on the market that do not contain oxybenzone and octinoxate, and many mineral sunscreens (physical blockers) that do not contain any chemical absorbers. You have myriad types and brands of sunscreen to choose from, most of which are now marked “reef-friendly.”

The bottom line with these sunscreen questions is that more research is needed to answer certain questions, but more research is not a reason to stop wearing sunscreen. Research is clear that UV rays are a major risk factor for skin cancer; skin cancer is the most common cancer in the U.S.; and melanoma is the deadliest form of skin cancer. Sunscreen is an important way to reduce the likelihood of developing skin cancers, including melanoma.

Is It True That Other Countries Have Sunscreen Ingredients We Don’t Have in the U.S.?

Yes. The next generation of photostable, broad-spectrum sunscreens that offer UVA and UVB protection has long been approved for use in European and other countries, but not yet in the U.S., with a few product exceptions. There are eight new sunscreen ingredient applications awaiting approval from the FDA, and those applications were filed between 2002 and 2009. Why the delay?

For one, it’s important to note that in the U.S., sunscreens are regulated as over-the-counter drugs; in Europe, they’re regulated as cosmetics. The regulation and approval process are different.

A second reason given by the FDA is that Americans have, over the last few decades, dramatically changed the way they use sunscreens, which is a good thing: We’ve gone from occasional use by a portion of the population to extensive, daily use by people of all ages, ethnicities, and complexions, and this increase in use is encouraged by the FDA to help lower the incidence of melanoma and other skin cancers. With this increase in use, it’s incumbent upon the FDA to make sure that any new UV filter that will be used so extensively is safe.

In 2014 Congress passed and President Obama signed the Sunscreen Innovation Act, which created a new process for the review of safety and effectiveness of nonprescription sunscreen ingredients, specifically the eight awaiting review. By March of 2015, the FDA determined that additional data was needed to support each of the eight new filters. So far, none are approved yet.

In 2019 the FDA also issued a proposed rule “to update regulatory requirements for most sunscreen products in the United States…The FDA is asking industry and other interested parties for additional safety data on 12 active sunscreen ingredients currently available in marketed products.” No new data is requested for titanium dioxide and zinc oxide, but data is being requested for the eight previously mentioned commonly used chemical absorbers (avobenzone, octinoxate, etc.) currently available in U.S. products (and some others not commonly used).

Again, the FDA’s position is that sunscreens are now worn daily and by people of all ages, including pregnant women and children, and the increase in use, as well as the above mentioned study about absorption, warrants their commitment to gathering further information. But again, as Janet Woodcock of the FDA said, even if an ingredient is absorbed through the skin and into the body does not mean that the ingredient is unsafe, nor does the FDA seeking further information indicate that it is unsafe. In fact, in July of 2020, the FDA made this point clear: “Absorption does NOT equal risk – The FDA advises continued use of sunscreens,” and noted that the further studies are intended to “fill in the current data gaps for these ingredients.”

Indeed, despite the FDA’s call for further data, the U.S. Surgeon General, the Centers for Disease Control & Prevention, and the FDA itself all encourage—in fact, the FDA “urges”—the use of sunscreen, and all cite the enormity of the melanoma and other skin cancer problems that the U.S. is dealing with as the reason to do so.

Bottom line: The data on twelve long-approved active ingredients are being updated, and the following eight “new” ingredients are still being reviewed:

Octyl Triazone
Drometrizole Trisiloxane

AIM hopes the FDA will come to a decision soon, as approval of any or all the ingredients would help consumers have access to a larger selection of sunscreens. Additionally, many in the melanoma world say several of these new filters are superior to what we have in the U.S., so approval means both a larger selection AND better protection from UV rays. That’s a win-win for consumers.